Spring ring for a piston ring assembly

ABSTRACT

A spring ring for a piston ring assembly has an H-shaped cross section with the radially inner projection thicker than the raidally outer projection which in turn is thicker than the connecting portion and lateral slits extend radially inward, alternately from the peripheral edges to a slight center overlap.

United States Patent [191 Minegishi [451 Oct. 30, 1973 SPRING RING FOR APISTON RING ASSEMBLY [75] Inventor: Hiroshi Minegishi, Kawagoe, Japan[73] Assignee: Nippon Piston Ring Co., Ltd.,

Tokyo, Japan [22] Filed: Jan. 8, 1971 21 Appl, No.: 104,877

[30] Foreign Application Priority Data Jan. 12, 1970 Japan 45/3371 [52]US. Cl 267/15, 277/139, 277/141 51 Int. Cl F161 1/34 [58] Field ofSearch 277/138, 139, 141;

[56] References Cited UNITED STATES PATENTS 3,353,830 11/1967 Bell..267/1.5X

656,562 Myers 277/139 2,776,865 1/1957 Anderson... 277/139 3,342,4769/1967 Vossieck.... 267/15 2,594,164 4/1952 Hedberg 267/15 PrimaryExaminerWilliam F. ODea Assistant Examiner-Peter D. FergusonAttorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A springring for a piston ring assembly has an H- shaped cross section with theradially inner projection thicker than the raidally outer projectionwhich in turn is thicker than the connecting portion and lateral slitsextend radially inward, alternately from the peripheral edges to aslight center overlap.

1 Claim, 7 Drawing Fignres SPRING RING FOR A PISTON RING ASSEMBLYBACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This inventionrelates to a spring ring used for the internal combustion engineequipped with a piston which has a piston ring groove of low axial depthnot exceeding about 3.5 mm.

2. DESCRIPTION OF THE PRIOR ART Oil scrape rings made of cast iron arewidely used for internal combustion engines, but have low tensilestrength because of their one-piece construction. Whereas, oil scraperings made of high grade alloys have sufficiently high tensile strengthbut are expensive. Besides, such oil scrape rings cannot have wide oilwindows due to their narrow thickness, and therefore the oil scrapingability of the oil ring is restricted. The design or the modification ofthe shape of the oil ring is also restricted by the existence of the oilwindows.

SUMMARY OF THE INVENTION The invention provides an improved spring ringmade of a steel plate which eliminates the aforesaid defects in theconventional oil scraping rings, and also provides a method of producingthe spring ring forming a portion of such an assembly.

More detailed embodiments of this invention will be explained withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of aportion of a spring ring for the piston ring assembly according to thisin vention.

FIG. 2 is a schematic view of a part of a strip formed into the springring of FIG. 1.

FIG. 3 is a plan view of the strip with a plurality of lateral slitsperpendicular to the length of the same.

FIG. 4 is a plan view of another strip with lateral slits.

FIG. 5 is a cross section of the strip of FIG. 4, further worked to formthe outer and inner projections.

FIG. 6 is a cross section of the piston ring groove of a piston,carrying both the spring ring and a pair of low thickness scraper rings.

FIG. 7 is a cross section of a spring ring of this invention with a Crplating layer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the springring of this invention has an approximately H-shaped cross section, andis composed of an outer projection having an upper supporting face 6 anda lower supporting face 7. An inner projection 8 has a thickness largerthan the thickness B of the outer projection, and a connecting part 3lying between said inner and outer projections has a thickness smallerthan the outer projection thickness B. A plurality of lateral slits aare cut from the outer periphery of the ring along the radial direction,to the middle zone of the connecting part. Also, a plurality of lateralslits b are cut from the inner periphery of the ring, along the radialdirection to the middle zone of the connecting part.

In the production of this spring ring, a steel or phosphor bronze plateor strip 4 having an H-shaped cross section and composed of an outerprojection 1, an inner projection 2, and a connecting part 3 with thethickness smaller than the thickness B of said outer projection, isfirst worked to form a plurality of lateral slits a from an outer edge 5of the rod to the middle zone of the connecting part and also lateralslits b from an inner edge of 5' of the strip to the middle zone of theconnecting part, as shown in FIG. 3. Each of the slits a and each of theslits b are mutually arranged one after another.

Then the worked plate or strip is bent into a ring so that the edge 5becomes the outer periphery. The formed ring has the structure as shownin FIG. 1.

Another method of producing the spring ring will be explained withreference to FIG. 4 and FIG. 5. A metal strip having a rectangular crosssection is worked to form a plurality of lateral slits a from one edge 5of the strip to the middle zone of the connecting part and also aplurality of lateral slits b from another edge 5 to the middle zone ofthe connecting part, as shown in FIG. 4. Then the upper face 13 and thelower face 14 of the slit strip are subjected to pressing, rolling,cutting or grinding to form the outer projections l, the innerprojections 2, and a connecting part 3 with a thickness lower than thethickness B" of the said outer projection, as shown in FIG. 5. Thedotted line, shows the starting cross section of the rod, and thehatched zone shows the cross section of the worked strip. After that,the worked strip is cut into the desired length and bent into a ring sothat edge 5 becomes the outer periphery. Thus, the spring ring as shownin FIG. 1, composed of the outer projections 1 having the upper andlower supporting faces 6 and 7, inner projections 2, and the connectingpart 3, is obtained.

Referring to FIG 6, a pair of thin scraper rings 9 are applied to bothsupporting faces 6' and 7' of the outer projection of the spring ring;this assembly of the spring ring and the thin rings is inserted into apiston ring groove 11 of a piston 10; and the piston 10 is inserted intoa cylinder 12.

As particularly mentioned above, a spring ring can be produced with caseaccording to this invention, and the thickness of the spring ring can beminimized by putting the latter between a pair of thin rings 9.Therefore, the spring ring of this invention is well suited forinserting into a narrow piston ring groove.

Besides, this spring ring has the following advantages:

1. The spring ring of this invention exhibits high tensile strength ascompared with the conventional cast iron oil scraping ring.

2. The spring ring of this invention fits well to the inner wall of thecylinder due to its flexible structure caused by the plurality oflateral slits.

3. The spring ring of this invention has a good oil scraping property ascompared with conventional cast iron oil scraping rings.

In order to increase the wear resistance of the spring ring of thisinvention and to smoothly flow the scraped lubricating oil, the surfaceof the spring ring carries a Cr plating layer 15, as shown in FIG. 7. Inaddition to that, if the spring ring of this invention is produced fromstainless steel, for example 17-7 PH steel, the mechanical properties ofthis spring ring are remarkably increased to fully eliminate breakingdefects.

While this invention has been described with reference to particularembodiments thereof, it will be understood that the numerousmodifications may be made by those skilled in the art without actuallydeparting from the scope of the invention.

that of the outer projection, and said connecting part between saidprojections having a thickness smaller than that of the outerprojection, and a plurality of narrow, lateral slits extending radiallyfrom the inner and outer peripheries of the ring in alternating fashiontoward the middle zone of the connecting part and defining therebetweenring portions of H shape cross section.

1. A spring ring for a piston ring assembly, said ring comprising: anessentially solid, continuous ring member including a radial connectingpart connecting outer and inner axial projections to each side of theconnecting part, said inner projection having a thickness greater thanthat of the outer projection, And said connecting part between saidprojections having a thickness smaller than that of the outerprojection, and a plurality of narrow, lateral slits extending radiallyfrom the inner and outer peripheries of the ring in alternating fashiontoward the middle zone of the connecting part and defining therebetweenring portions of H shape cross section.